pythran: Unable to configure CC and CXX in pythranrc and gcc 7 bug with pythran+numpy

System configuration

• Arch Linux
• gcc-7.1.1 and gcc-5.4.0
• numpy==1.13.0
• pythran==0.8.0
• python==2.7.13

First of all, allow me to rant that it should be mentioned somewhere in the README that pythran only works in a medium version gcc > 4.9 and gcc < 6(??). I lost quite a lot of time trying to pythranize with gcc==4.7.2 and gcc==7.1.1 (super old and super new) - does not work at all (for traceback, see https://paste.pound-python.org/show/bA0TjMrAWP54PcKOU375/ ).Thanks to folks at IRC channel #pythran I was able to figure this out.

Issue

Pythran works when I try

$ CC=gcc-5 CXX=g++-5 pythran nd_local_maxima.py

on the test case.

However when I try to make this choice of compiler permanent by modifying your pythran-linux2.cfg template and putting it in $HOME/.pythranrc as follows:

[compiler]
defines=USE_GMP
undefs=
include_dirs=
libs=gmp gmpxx
library_dirs=
cflags=-std=c++11 -fno-math-errno -w -fwhole-program -fvisibility=hidden
ldflags=-fvisibility=hidden -Wl,-strip-all
blas=cblas
CC=gcc-5
CXX=g++-5

Note that, leaving blas option empty gave me some other weird error. On running:

$ pythran nd_local_maxima.py -v

yields a type error.

running build_ext
running build_src
build_src
building extension "nd_local_maxima" sources
build_src: building npy-pkg config files
new_compiler returns distutils.unixccompiler.UnixCCompiler
INFO     customize UnixCCompiler
customize UnixCCompiler using build_ext
********************************************************************************
distutils.unixccompiler.UnixCCompiler
linker_exe    = u'gcc-5'
compiler_so   = u'gcc-5 -fno-strict-aliasing -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -DNDEBUG -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -fPIC'
archiver      = ['ar', 'rc']
preprocessor  = u'gcc-5 -E'
linker_so     = ['gcc', '-pthread', '-shared', '-Wl,-O1,--sort-common,--as-needed,-z,relro']
compiler_cxx  = u'g++-5'
ranlib        = None
compiler      = u'gcc-5 -fno-strict-aliasing -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -DNDEBUG -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong'
libraries     = []
library_dirs  = ['/usr/lib']
include_dirs  = ['/usr/include/python2.7']
********************************************************************************
new_compiler returns distutils.unixccompiler.UnixCCompiler
INFO     customize UnixCCompiler
customize UnixCCompiler using build_ext
********************************************************************************
distutils.unixccompiler.UnixCCompiler
linker_exe    = u'gcc-5'
compiler_so   = u'gcc-5 -fno-strict-aliasing -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -DNDEBUG -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -fPIC'
archiver      = ['ar', 'rc']
preprocessor  = u'gcc-5 -E'
linker_so     = ['gcc', '-pthread', '-shared', '-Wl,-O1,--sort-common,--as-needed,-z,relro']
compiler_cxx  = u'g++-5'
ranlib        = None
compiler      = u'gcc-5 -fno-strict-aliasing -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong -DNDEBUG -march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong'
libraries     = []
library_dirs  = ['/usr/lib']
include_dirs  = ['/usr/include/python2.7']
********************************************************************************
Traceback (most recent call last):
  File "/scratch/avmo/opt/fluidsim-merge/bin/pythran", line 11, in <module>
    sys.exit(run())
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/pythran/run.py", line 133, in run
    **compile_flags(args))
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/pythran/toolchain.py", line 360, in compile_pythranfile
    **kwargs)
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/pythran/toolchain.py", line 331, in compile_pythrancode
    **kwargs)
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/pythran/toolchain.py", line 293, in compile_cxxcode
    output_binary, **kwargs)
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/pythran/toolchain.py", line 263, in compile_cxxfile
    '--build-temp', buildtmp,
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/numpy/distutils/core.py", line 169, in setup
    return old_setup(**new_attr)
  File "/usr/lib64/python2.7/distutils/core.py", line 151, in setup
    dist.run_commands()
  File "/usr/lib64/python2.7/distutils/dist.py", line 953, in run_commands
    self.run_command(cmd)
  File "/usr/lib64/python2.7/distutils/dist.py", line 972, in run_command
    cmd_obj.run()
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/numpy/distutils/command/build_ext.py", line 206, in run
    self._cxx_compiler = compiler.cxx_compiler()
  File "/scratch/avmo/opt/fluidsim-merge/lib/python2.7/site-packages/numpy/distutils/ccompiler.py", line 633, in CCompiler_cxx_compiler
    cxx.compiler_so = [cxx.compiler_cxx[0]] + cxx.compiler_so[1:]
TypeError: can only concatenate list (not "unicode") to list